Female? Smoker? What you should know about alcohol consumption - International Scientific Forum on Alcohol Research Critique 215

The latest ISFAR critique looks at research into alcohol consumption by elderly female smokers

While essentially all epidemiologic studies have shown adverse health effects of cigarette smoking and beneficial effects of moderate alcohol consumption, a recent study in this area that followed a cohort of elderly women into very old age proved interesting reading.

The research comprises a prospective cohort study of 9,704 women at least 65 years of age, who were living independently at baseline and were not heavy drinkers; they had a mean baseline age of 71.7 years (range 65-99) and underwent repeated assessments of lifestyle habits starting in 1986 to 1988. They were followed longitudinally until death, loss to follow-up, or to April, 2016.

Outcomes included grip strength, walking speed, prevalence of threshold scores for self-reported health, difficulty with three or more instrumental activities of daily living (IADLs), depression, prevalence of falls, living in a nursing home, and death after 10- or 20-year follow up. The main comparisons evaluated in this study were between women who were smokers and those who consumed alcohol moderately, with each analysis adjusted for the other exposure.

ISFAR members considered this to be a well-done study that provides some important data relating effects of smoking and moderate drinking on function and mortality in very elderly subjects (an age group where data are lacking). There were criticisms, however, that the study does not report the effects of moderate drinking among smokers; previous studies have shown that the adverse effect of smoking is modified by moderate alcohol intake.

Further, given that the reasons why some women quit drinking during follow-up are not known, the article does not contribute to clarification of the problem of reverse causation (eg, healthier women may tend to continue drinking whereas sicker women stop alcohol consumption). Also, the authors did not adjust for some strong confounders, especially those related to socio-economic status.

Nevertheless, the results of this study make a real contribution to our knowledge of the effects of drinking on both quality of life and mortality among women who are 65 years or older. The follow-up of subjects continued for at least 20 years, by which time almost 70% of the women had died. Hence, the effects on mortality should be excellent estimates.

As expected, women who were smokers had greater risk for almost all adverse outcomes, while drinkers who continued to consume moderate alcohol into old age had the most favourable outcomes. While the authors report that women who reported drinking at baseline but quit later on had mortality risks that were intermediate between non-drinkers and persistent drinkers, the reasons why some women quit drinking were not known.

Hence, it is appreciated that continued drinking could be only a marker of better health, and not the cause.